A galvanic isolator provides a means for moving a signal from one electrical circuit to another electrical circuit in a control system when the two electrical circuits should otherwise be electrically isolated from one another. Usually the two electrical circuits operate at different voltages, and thus, should be electrically isolated. For example, consider an application in which a 5V battery powered controller board is configured to control a motor circuit operating at 240V. In this example, the 240V motor circuits should be electrically isolated from the 5V controller circuit, while permitting the 5V controller circuit to send or receive signals from the 240V motor circuit. In this type of application, an isolator may be used to provide voltage and noise isolation, while permitting the information exchange between the two circuit systems. Opto-isolator, also known as optocoupler, is one of the most commonly used galvanic isolators.
Generally, an optocoupler comprises an optical emitter and an optical receiver. The light emitted by the optical emitter may be transmitted to the optical receiver either via reflection, or directly from the optical emitter to the optical receiver. A portion, or more specifically a photo-detector portion of the optical receiver may be configured to receive the emitted light. In order to obtain the highest efficiency, it may be desirable to channel as much light as possible from the optical emitter to the photo-detector.